Add libcaffe.a to dependencies for TEST_ALL_BIN

Prior to this change, running `make clean && make test` gave the error `g++: error: libcaffe.a: No such file or directory`.  This fixes that.

Edit: `make clean && make runtest` was giving a similar error `g++: error: build/src/gtest/gtest-all.o: No such file or directory`; commit 9251ae7 fixes that as well.